Safety arrangement for x-ray apparatus



Dec. 27, 1949 M. F. HALL 2,492,281

SAFETY ARRANGEMENT FOR X-RAY APPARATUS Filed March 29, 1945 2 Sheets-Sheet 1 M/? w/v 75/9522 I :1 1/611 tor m Q Attorneys Dec. 27, 1949 M. F. HALL 2,492,281

SAFETY ARRANGEMENT FOR X-RAY APPARATUS Filed March 29, 1945 r 2 Sheets-Sheet 2 4 a; E- f 5 g a 9 /03 MRWNFZZZL L Inventor f; jam-406:

Patented Dec. 27, 1949 UNlTED STATES PATENT; OFFICE SAFETY ARRANGEMENT FOR X-RAY APPARATUS Marvin F. Hall, Joplin, Mo.

Application March 29, 1945, Serial No. 585,472 Claims. (Cl. 250- 93) This invention relates to X-ray apparatus and it has particular reference to safety arrangements for preventing overdosage when handling equipment of this type for therapeutical purposes.

Means for finding and applying the correct'dosage for the treatment of some tissue or of some part of the human body and means for controlling the emission of X-rays from the Roentgen tube in exact accordance with the calculated dosage as found have been developed to such a degree that errors in this respect have become unlikely, provided the various prescriptions as to the handling of the dosimeters and of the equipment are followed to the letter. It is however unavoidable that accidental errors occur now and then. By this term a type of error is designated which cannot be remedied by the above-mentioned control and safety appliances as it is an error due to the omission to operate, or to inadvertent or mistaken operation of one of the control levers, knobs or appliances while hane dling all the other controls properly in accordance with the desired dosage. The error is therefore due to incomplete or inconsistent handling of the apparatus while trying to follow the regular pattern of prescribed activities.

The number of such accidents will largely depend on the experience of the persons handling the apparatus, but accidents of this type can never be eliminated completely if a large number of treatments is administered by a number of persons, skilled as they may be. Experience shows that the number of such accidental overdosages is much larger than is usually supposed; for a large percentage of these accidents does not lead to harmful or to disastrous or to easily visible consequences. The real percentage of accidental incorrect treatment reveals itself merely ,if each treatment is carefully checked.

On account of the small number of cases with disastrous or manifest consequences little has been done at present to exclude such accidental false dosage and especially overdosage or to render it harmless.

The main object of this invention, therefore, consists in anarrangement which prevents such accidental errors and which especially prevents overdosages due to mistakes of commission or omission, thus cutting down the risk of causing damage to some tissue by accident.

- A further and more specific object of the invention consists in providing circuits associated with the X-ray controlling means and especially with the means controlling the voltage applied to the X-ray tube which do not permit the application 2 of such high voltage unless other means are properly set. p

A further and specific object of the invention consists in providing circuits associated with the filters to be used during therapy treatment which prevent the use of a high tension voltage without filter or together with filters which are not suited to the voltage selected.

It is a further object of the invention to provide filter test and control circuits allotted to the filters and controlling the current supply to the high tension X-ray tube circuits which permit the application of high tension to the tube merely in connection with a properly selected filter. 1

It is a still further object of the invention to provide a filter arrangement with filters each of which has an individual characteristic shape or equipment adapted to operate one filter circuit, each of said circuits controlling the high tension current supply to the X-ray tube but each being only closed when a proper high tension voltage has been selected.

It is a still further object of the invention to provide an X-ray arrangement the high tension current supply of which is made adjustable in a series of steps by means of a selector and to further provide a number of filter test circuits each adapted to be closed by one filter only and moreover associated with the selector in such a way that the said circuit is only closed when a definite voltage has been selected on the selector, the circuit thus controlled by the nature of the filter selected and by the voltage selected con trolling the high tension current supply to the X-ray tube. V I

It is a still further object of the invention to include the timing switch into the control exercised by the filter test circuits, so that said switch can be only operated when the filter circuits permit operation of the X-ray tube, this inclusion preventing errors as regards the actual application of a dosage of X-rays which might otherwise erroneously have been listed as applied while the filter test circuits prevented such application.

Other objects of the invention will be rendered apparent in the following detailed specification describing one embodiment of the invention which is also illustrated in the accompanying drawings.

It will be understood however that the present invention relates in first place to the system and that the details, components and parts may be varied in many ways without departing from the essence or'spirit of the invention.

Special mention in this connection may be made of the fact that the commercial types of X-ray equipment for therapy show a number of widely difierent circuit arrangements. Each can be adapted in the way shown, but each has to be adaptedw'ina difierenhway, usinggtsindividual way of regulatingihehigh tension voltage/and its other individual equipment.

The same X-ray equipment may be provided; with exchangeable filters in several different ways, only two of these ways beingaillustrated;

But every other way of using filters may be-in-- cluded in the presently described system More:

over, filters have been illustrated closing the test circuits by virtue of special zdifllerences in their outline, but it is manifest that mere differences,

and manufactured as a standard equipment which has} been adapted for-purposes= oi the present invention:

Figure 2' isa perspective view of -one filter element as used in connection with equipment associated withthe X-ray ti-1136:

Figured is a top view -of a scriestof filter ele.- ments showing the varying configuration which is used for closing individual circuitsandiurther showing; means for. preventingizimproper; insertional Figuret-iisla perspective-ali n!i howin th o.- operationiofithe filter elemen al-with; circuit clos; ing. elements: V

Figure iss u.r ev t nal l ecti r ale w t ter ement n i re :1 el-di e aiee ll fi err a en oi the turret -typc filter nead which may; be eq nted naiX r ub a semb r fowerfiain ype oi work- The embodiment. of.v the inyention asillustrated in Figure l is based on an X-ray equipmentior he cei t anm es hich c ll man factured,, and is, well knqwn and it is therefore unnecessary to describe; or illustrate ,7 in detail thos parts, e ements, components a d. c nnections wl1ic h are not directlyrconnected with the present e t qn.

These known parts whichare to be found in various modifications in allx rayarrangements re he i-reyw e l th n e I he filament'heating current-regulator 12; the voltage regulatoror selector l3, the low tension transformer or auto-transformer 4 and the high-tension transformer l; Thecircuit also contains the customary amme ter and voltmeter.

The selector switch l3*is provided with a con- 1 1 arm c rcqnia t ment dtact bank l8 of 'a voltage selector'with-a number 01, contactso, b,;c,-k l,-m,- each 'connected with one of the tapped'windin gs of the "low tension or 4 auto-transformer (4. According to the invention this contactor switch is moreover provided with an additional contact segment [9 and an additional contact bank 20 of a filter selector, provided with contacts n, o, p, y, a. The contactor is provided with conducting strips or bridge pieces 2 I 22 for connecting the contact segments I Ti, l 9 with the contacts of the respectiye contact banks :8, 20, while the, contactor; segment I! is connected with the primary of the high tension transformer [5. The additional contact segment [9 is connected with a circuit 2|, containing a relayl23, operating contacts 24a, 24 located in the control circuits 25, 26 which in the example shown contains the timing device II. The latter consists of a synchronous timing motor 33 inserted incircuitr25rand; When actuated, closing contact 320i circuit 26 which contains the magnetic contactor or relay 3| controlling the primary circuit of the high tension transformer I5, by means of contacts 29; 305i The segment l 9; as has been mentioned; coopcrates with the-contacts n; o, p -a2, yyz-of th'e contact" bank -25) and these-contacts which are provided forthe purpose of: matching==v thecfilters selected with the voltage of-thehigh tension currents are hereinaften termedmatching con-e, tacts. They are --c0nnected 'witlrthe filter: con tacts i l (grand with indicatorlamps -61 62 allotted to each filter contact,"

The -filter contacts 14!, 42-are operated by :the filters 1|, 712' one 'of -which is illustrated ibyzway of examplein Figure 2;" Each filter I is provided with a projection, lug orfl-tonguef the; exact location of which varies 'as clearlyrshown in Fig, ure 3, representing-a number offilters; of vari-' ous filtering powersuch: as :used.:during.-.therapy work. The filter may moreoverbelprcvided with a-projectingportion or ledge 8| :which in -th'enexrample shown is shorter than" the-overall length ofthe filterllt therefore providesla' corner. 83 which has to fit into a -recessw-84 lot the framework-85 receiving the filter.- It is seen that the smallerend-section-of the-filter can only be pushed intothe right position when the-filter is inserted correctlywith the tongue pointing c for.- ward; for" an insertion with the-tongue pointing backward would: not a1lo-w-the-filter-to slide in and theoperator-would thus immediately 'bemade awareof the fact .that the filter is not in a correct position. This holdsalso. good when the filter is inserted with-thetongue pointingin the right direction but with the lwrongtside of. the filter pointingupwardly. The ledge 8lsthus prevents any incorrect insertion: of ltheJ-filter, which would affect the" correct position of "theilugl or tongue -80 and? secures positively-:the right position of the-tongue. The lug or-tonguecooperates with the row of filter springs 4 I:,-I42:and:the. filter is grounded-or connected with the casing-or with some other convenient point-of the apparatus which: is grounded and whenxathje filter is .insorted one or" the springs M 42 whichicomes; into contact with its tongue will be connected with ground and will: complete thelfilter checking circuit connectednwith the matching.::contacts. 20 and with segment I92 The. energizationof this circuit will put the timing device in readiness for action.

One of the filters -l' I" used may not be. a filter but maysimply-be a'framerprovided withzawindow or opening or with asubstancewhichis permeable for-the X=raysand through which unfiltered X-rays may penetrate The .useoi rays without filters is thus included intothe safety applied by timing the contactor arm It to a given contact for instance to contact is merely possible with a filter which corresponds to this voltage. For the switching in of the exciter voltage corresponding to the desired kilo voltage also switches in a definite filter circuit connected with a filter matching this voltage and controlling the control circuits of the tube. Merely if and when the filter circuit is actually closed by the insertion of the right filter the control circuit of the X-ray tube is completed and permits operation .of the X-ray tube and X-ray emission.

To make this clear the operation of the device in the case of an example will be described. Let it be assumed for instance that a filter of /2 mm. Cu.l mm. Al has been selected by the radiologist for the therapy in question and that this filter according to the dosage computation cooperates with a voltage of 140 kilovolt. When the filter has been correctly inserted in the example here adopted (it is the filter 12) it will be in contact with filter spring 42 and will be grounded. When the selector is turned to contact I), which is assumed to be the contact producing a kilovoltage of 140 kv., a circuit will be closed from lead 90 connected with one side of the auto-transformer I4 over conductor 2I, relay 23, segment I9, matching contact 0, filter checking circuit branch spring 42 and filter I2 to ground. Simultaneously, the lamp indicator I52 will clearly show that the circuit is completed and that the right filter matching the voltage selected has been inserted. The operator may set the time switch II and operate it as usual for by virtue of the completion of the circuit 2I relay 23 has been operated and has closed the circuit 25 leading to the synchronous motor 33 of the timing device II and the circuit 26 leading to the contact 32 operated by the time switch II. When the latter is now operated, and its operation upon pressing of the starting button is audible, the contact 32 will be closed and the magnetic contactor 3| is energized which closes the two contactor arms 30, 29 of the circuit of the primary of the high tension transformer I5, thus operating the X-ra tube for the desired time period.

Assuming that a wrong filter has been placed in front of the window of the X-ray tube; thena spring, for instance the spring M, is in contact with the filter; but as the selector arm I6 stands on contact n corresponding to the selected kilovoltage of 140 kv. the circuit of relay 23 is not closed and the timer remains disconnected.

It is, of course, possible and in some instances it may be preferable to arrange the contacts of relay 23 in the circuit 21, 28 of the primary of the high tension transformer. This eliminates however one of the controls exercised as in this case the timing switch, when operated, would seem to function while indeed the circuit of the X-ray tube has not been closed. The supervision in this case would have to be exercised solely by means of the indicator lamps, as no lamp signal is given when the proper filter corresponding to the voltage selected has not been inserted.

The constructions of the filters may be varied and may be adapted to the various purposes. It is, for instance, in many cases necessary to use filters with a variety of voltages which may be contained within wider limits than those set by the voltage steps between the voltage controller contacts. In this case the projection or tongue 00 is made wider than one spring so that it will be in contact with several springs II, 42 simultaneously. If safety is to be maintained at the intended degree, the width has to be so arranged that no voltage likely to do damage is included. It will be seen from the above description that the hazards of an incorrect or inconsistent manipulation of the various appliances or controls are minimized. The greatest possible error would be to overlook entirely the resetting of the machine when patients change and to treat one patient with the adjustment that has been made for another. Practically no really disastrous consequence can occur in this way however. The greatest difierence in the dosage, which is possible, occurs when changing from a low voltage treatment without filter as prepared for superficial treatment to medium or deep therapy with filter to be applied to another patient. If the very gross error is made of preparing everything with the exception of voltage and filter, a double error which is most unlikely, to occur, the possible overdosage, assuming exposure for the same period, would be only /5 or 6 of the overdosage which is easily possible Without safety device.

The device if constructed in the way described with a filterless window forming one of the contact making appliances which are part of the security scheme prevents therapy without filtration with a voltage higher than that regarded as safe when the device was originally set. Similarly, the device prevents operation when filtration and voltage are not matched. 7

Many X-ray machines use a turret type filter head or may be adapted for such use. The invention may be applied to this filter head without difficulty as illustrated in Figure 6. Turret type filter heads are used, as a rule, in connection with a tubular shielding and guide tube and are rotatably arranged, all the filters being arranged on the rotatable member, and are brought into correct operative position with respect to the beam by rotating saidmember.

To apply the invention the filter carrier IOI (Figure 6) arranged within the turret head I02 is provided with the requisite number of filters, I03, I04, I05, I06, four being shown in the drawing, and may rotate around a shaft I01. The turret head is arranged eccentrically with respect to the beam guiding and shielding tube I08. Each filter is again provided with a lug or tongue I23, I24, I25, I26 located on its periphery arranged at different places along the are forming said periphery as clearly shown in the figure and cooperates with a spring I I0 which forms part of a series IIO, III, H2, H3. Contact is established by the lugs or tongues I23, I24, I25, I26 with one individual spring of said series only when the filter is moved to the operative position covering the beam tube I08. In this case the lug or tongue comes into contact with one of the springs and completes the circuit which is otherwise identical with that shown in Figure 1. If removable combination filters are used the filters should be fixed to each other by riveting or otherwise to prevent mistakes. In turret filter heads where filters forming a combination are used which are sometimes arranged on superposed filter carriers each of which is separately movable, the carriers may all be provided with tongues, as described, and may cooperate with springs,as illustrated, pairs of springs being preferably used with the control and matching circuit wired over the aeaica ncl 7 springs fat :the combination cor vcombinaticns matching the highitensionwoltage.

Finally, it may be rnent'loned L'that iita'is a possible, although l iai dly adv-isable, -to :arrange =a master contactor sw itch permitting the 'radiolo- -gist I to administer larger doses within 1 a :short tin-1e; switches of this -typeareinoiwnsed to treat without filter at lcw' kilovolta'g'es. Suc'h a-switch or contactor even if provided with --'-security means introduces howevera definite hazard; its

arrangement -should -theref-ore be confi'ned to thosecases in whioh tlie 'taki ngof 'risksrisnec- "essary' to accomplish results?which 'a1'e:otherwise nnobtainable.

'I claim:

'1. A :saiety system if for i excluding dosages in X-ray apparatus, :comprising an X ray tube, mea-ns to supply said tube with high tension ciirrents of different: voltageaineans foriproducing step by step regulationcofosaid 'voltage,- said nieahs including "a voltage selector having aset of fixed voltage selector :contacts, 'each corresponding i to an opetational voltage :supplied to the K-ray tube I further having-"a -movable contact member for selecting :sa fixed co-ntact, "corresponding to adefiriite=voltage, anumber of filters 'of 'difierent filtering-power adapted to 'beinse'rted into the ,path of-the X-ray beams, -filter checking "contact closing :means on *each filter occupying diiierentipositionsonfilters of -difierent filtering power, 1a :filter :selector, in- =cluding fixed filter selector contacts, :a filter checking circuit branch -connected with each filter selector contact, a fixed --iilter checking contact in said "filter 'checkingcircuit branch adapted laccooperate 'with the filter checking contact closing means ci a filter: of definite-filtering power occupying a definite position on said filter, said filter selectormoreover 1 including amovable'contact member cooperatingwith the-fixed filter :selectcr contacts, -a commoncircuit branch for all the filter checking circuits, a control device for themeans for supplying the X-ray tube with high tension current and a positive permanent mechanical connection between the movable contact membersof the; voltage selector and the movable contact member oh the filter selector coordinating automatically the f llter selection and 'thevoltage selection of the -X- ray tube, the operationofthe X -raytube-being dependent -on the selection of-a safe voltage filter combination. 1

2. A safety systemior excluding closage :er- -rors-in- X-ray apparatus, comprising an ii -ray -tube, a surroundingbcxiprovi-ded with an outlet for-the X rays, ineans for-supplyingthe-said Y X-ray tube withhigh tension currents-of different voltages,- a voltage selector, including a set of fixed voltage selectorcontacts andan adjustable movable-contact member,- cooperating wvith theset-of fixed-contacts, voltage selecting circuits connected with the means to supply X- ray tube V with high tensioncurrenta-a number of exchangeable filters :adapted to be inserted into thebox for-filteringthe X-rays emanating 1 from the outlet of thebox each filter'being: providecl; with contact closingfilter checking means arrangedin a definitepositionon-the-filter said positions being different afor- -filters of --'ditierent filtering powerrafixed-filterchecking contact-in said box for eachof said--filters; =a filter checking circuit branch connected with each of said-fired contacts in the box, a filterselectonincluding a set of fixedselecton contacts,- a'rcommom segmentand a movable contact 'member for con- 8 zinecting one 'o'fi said fixed filter: selector contacts With"the common isegment, each fixed "filter-selector contact of the set'being connected with one of the "filter checking'circuit branches; a

. common circuit branch connected withsaidcom- "mon segrnent, a "control relay means 'in said common branch for controlling the meansto supply the X ray tube with high tension currents, a movable contact" arm carrying the mov- -able 'contact-members of both the voltage se- :lector and ofthe filter selector, said arm being arranged for bringing its movable contact mem- "bers simultaneously into contact with one of the fixed contacts of thetwo 'selectors'in order to select simultaneously a voltage selecting circuit and a filter checking circuit branch, the'latter when closed by a filter 1 and :connected with the common branch operating -the-coritrol-frlay means' for supplying currentto the X-ray' tube.

safety system for protection against dosage errors in X-ray apparatus, comprisingan X -ray tube, means: for supplyingithe same with high tension "currents of difiererit voltages, a voltage selector-having a set of fi xed "voltage selector contacts ancl a movable voltage selectcr contact-member for selecting alpredetermindd operational voltage for' the X ray tube, a con- 'trol 'means'for the high? tension supply means-6f the X-ray tube, exchangeable filters ;.provided 0 with :circuit closing I means =-located :on "the: filter at 'aipoint characteristic for the' filteri-power of i the 'filter, 1 separate eircuit for- 'ea'ch predetermined operational voltage of the X-ray tube, each circuit being connected with one contact 'of said voltage selector, a filter holder, 3, filter selector, including a set 'of fixed contacts and a movable contact member cooperating with' -the 'said fixed contacts, means for 'mecha'nicallycou- .p'ling the movable contact member of'the voltchecking circuit branches-associated with each of said fixed filter selector contacts,-.--each-*circuit branch being provided withcircuitcloslng means 'closed -by the circuit i closing means of a filter upon-insertion of the same, the=i=nsertion' ofa filter"of definite filterapowerinto the filter holder, closing one ofsaid circuit' branches, -an operational circuit for-the high tension sup- ;ply control means-:ofthe Xii aytube;closable'by 1 the movernent of the f movablecontact member of the filter selector -to=a=contact;con-neotedwith a "filter checking circuit branch clo'sedi by a filter, the operation of the X raytube' bei-ng' thus de- 2 pendent on the use ofa safe filtervoltage-combination.

4. 'A safety system for protection against dosage I errors in X ray apparatus, comprising-anX-ray tube,- means for supplying: the same with high tension cur-rents; a voltageselectorwith fixed contacts and a movablecontdctrnember for selecting a predetermined operational voltage for-the X-'ray tube, a controlmeans for-the high tension supply means-ofthe X-ray tubeya 'box surrounding-said Xray tube and provided-with -ainvoutlet for-the X-rays,' a filter holder in said outlet; filters-with individual circuit closingcontact-means; each contact means beinglocated on saidfilter :in a position characteristic forthefiltering-mower of-said filter a fixed contact on-sa-id'filter holderiadaptecl to cooperate-with'thecontact closing means'on one of the-filters usableinthe hxjlder, a filter checking-circuit branch for each fi lter saidbranch "being connected with theaioresaid fi xed contact ofthe holder'a-nd closed bythecooperation of; the con-tact with-the contact-closing means ora filter.

a filter selector including a set of fixed contacts and a movable contact member, each of said filter selector contacts being connected with one of the filter checking circuit branches, a mechanical coupling means between the movable contact members of the voltage selector and filter selector, a seperate circuit for each predetermined operational voltage of the X-ray tube, closable by the contact of the movable member with the fixed contact of the voltage selector, an operational circuit for the high tension supply control means, a timing device controlling said operational circuit, means for supplying current to said timing device, control means for the last mentioned supply means, an operational circuit for the said control means, said circuit being controlled by the adjustment of the voltage selector and by the insertion of a filter into the filter holder, corresponding to the voltage selected, said correspondence being produced by the closing of one of the filter checking circuit branches connected with one of the filter selector contacts and by the selection of a corresponding position of the coupled movable contact members of the two selectors.

5. A safety system for protection against dosage errors in X-ray apparatus comprising an X-ray tube, a box with an outlet for the X-rays, a filter holder on said outlet, filters adapted for insertion into said holder, each filter being provided with a contact means located at a point characteristic for the filter power of the filter, means for supplying the X-ray tube with high tension current of different voltages, a relay controlling the supply of the X-ray tube with high tension currents, an operative circuit for said relay, a timing device with timing contacts, the latter controlling said relay, means for supplying said timing device and said timing contacts with low tension currents, a further control relay controlling the low tension current supply to the timing device and timing contacts, an operational circuit for the last named control relay, a voltage selector having a set of fixed contacts arranged in a circle and a movable contact member rotatable around the center of said circle, a filter selector having a set of fixed contacts arranged in a circle concentric to the aforesaid circle, circular seg- 10 ments concentric with each of the sets of fixed contacts, a single rotatable arm carrying both movable contact members, insulated from each other, individual contacts of the two sets of said contacts being overrun simultaneously by the movable contact members on said arm, a common circuit branch connected with the common segment of the filter selector forming part of the operational circuit of the control relay for controlling the low tension current supply to the timing device and contacts, a fixed filter checking circuit branch connected with each fixed contact of the filter selector, filter checking contacts in each of said filter checking circuit branch, each adapted to cooperate with the filter contact located at a definite point characteristic of the filter power of said filter, to close the filter checking circuit branch connected with one of said fixed filter selector contacts upon insertion of the filter, said closed filter branch being adapted to complete the operational circuit of the control relay for controlling the low tension current supply to the timing device, when connected, by way of the movable contact of the selector with the common circuit branch, the selection of an operational voltage of the X-ray tube thus entailing a selec-- tion of a definite filter selector contact and of a definite filter checking circuit closable only upon insertion of a filter of definite filter power.

MARVIN F. HALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,449,357 Waite Mar. 20, 1923 2,094,103 Horsley Sept. 28, 1937 2,225,940 Grossmann Dec. 24, 1940 FOREIGN PATENTS Number Country Date 366,925 Germany Jan. 13, 1923 487,665 Germany Dec. 14, 1929 506,758 Germany Sept. 8, 1930 

